The present invention relates generally to a method and system for crushing glass articles such as glass bottles etc., for disposal, and particularly to a method and apparatus for forming glass sands which may be effectively used as aggregates for road pavement, colored paving materials for walkways, traffic controlling white line markers to be applied on an asphalt cross-walk, various grinding materials, matrix material for potters, construction materials such as outer walls, block materials and in other application, in substitution for natural sands, by crushing glass articles for a disposal purpose.
Traditionally it has been a common process to crush used glass bottles etc., and use them as a material for reclaiming glass bottles etc., while discharging other portions which have been finely crushed together with a washing water so that they may be disposed as industrial waste materials. However, it has been proved to be advantageous if such stock materials which have been disposed as industrial waste materials so far after they are crushed into fine fragments is used as aggregates for road pavement, colored paving materials for walkways, traffic controlling white line markers to be applied on an asphalt cross-walk, various grinding materials, matrix material for potters, construction materials such as outer walls, block materials and in other application, in substitution for natural sands which have been used extensively.
In a current situation in which an excavation of natural sands may accelerate the environmental destruction and ruin the natural ecology, such production of glass sands come to play a vital role in preventing the destruction of nature.
Consequently, the applicant has disclosed a novel method and apparatus for producing glass sands from glass bottles etc., which can be used effectively in substitution for natural sands, while ensuring an easy handling without the risk of piercing operators"" hands etc., by processing them such that sharp crushed edges may be changed into smooth crushed surfaces (see U.S. Pat. No. 5,775,604, Japanese Patent Application Laid-open No. 9-99250).
In this prior art, as shown in FIG. 15, the glass articles 1 such as glass bottles etc., are supplied by means of first transfer device 2 into a primary crusher 3 where the glass articles 1 are crushed by means of crushing means 4, and then delivered to a underlying delivery section 6 via a sorter 5. The sorter 5 is adapted to sort out papers such as labels etc., and metallic or cork-made caps etc., which would stick to the glass articles that have been crushed, as well as glass fragments which have been insufficiently crushed to retain dimensions larger than those specified in the crusher 3, and then to discharge them out of the primary crusher 3.
The crushed articles 7 which have fallen into the delivery section 67 are then supplied to a secondary transfer device 8 by means of magnetic screening-transfer device 7. At this step, iron caps, nails and other ferrous fragments, which might be entrapped, may be removed into a ferrous-fragment container 9, by means of magnetic screening-transfer device 7. Then, crushed articles are fed into a secondary crusher 10.
In this secondary crusher 10, a container section 11 receives crushed articles and a crushing section may act to crush the glass material into finer fragments. Finally, sieving means 13 sort and deliver the articles which have been crushed, according to their grain sizes. The secondary crushing means 14 in the secondary crusher 10 are designed such that a blade may be arranged with a space narrower than that in the crushing means 4 of the primary crusher 3 and/or that it may rotate with a higher number of rotation. Furthermore, the crusher is equipped with a dual crushing means as shown in the drawing and may crush the glasses into fragments smaller than those of glass articles as crushed in the primary crusher, while at the same time rubbing glass fragments against each other so as to form approximately a spherical configuration and change sharp edges of these glasses which have been crushed into smooth ones. The secondary crusher 10 is connected with a dust collector 15. The sieve means 13 serves to return the glass powder which has not passed through the uppermost sieve back to the secondary crusher 10 by means of return transfer device 16 and secondary transfer device 8. The glass powders with approximately round crushed surfaces which have not passed through the sieve in the next lower stage-sieve may be used in substitution for natural sands on the walkway, and the glass powders which have not passed through a further lower stage-sieve may be suitably applied, for example, as aggregates of asphalt. Moreover, the glass powders which have passed through this sieve may find its"" application as construction materials, grinding materials or road paving materials. The glass articles dropped from the sieve device without passing through each of sieves are transferred to a paper-sorter 17 via a return/transfer device 16 just in the same way as that for the glass articles which have not passed through the first sieve, where they are separated into glass articles and labels etc., and then returned back to the secondary crusher 10 again by means of secondary conveyor 8. By repeating such actions as above-described, the glass sands which are sorted into three classes may be produced, depending on their grain-sizes.
FIG. 16 is a view disclosing an entire system which is arranged from the first crusher to the secondary crusher in a vertical configuration. Since each of the units is substantially identical to those as shown in FIG. 15, they are indicated by the same reference numerals of FIG. 15 with the letter xe2x80x9caxe2x80x9d affixed. The glass articles 1a such as the glass bottles etc., are supplied to the primary crusher 3a by means of first transfer device 2a and caused to be crushed under action of the crushing means 4a such as rotor etc. Subsequently, the glass articles are supplied to the secondary transfer device 8a via the sorter 5a (7a), and then transferred into the secondary crusher 10a where they are crushed into finer fragments, and finally are sorted and discharged by sieve means 13a according to their grain sizes. In the meantime, reference numerals 16a and 17a represent a return/transfer device and a paper sorter respectively. There is landing 18 which is used by the operator during maintenance of the system. Since working operations are carried out while the articles are being moved by gravity from upper portion to lower portion in the embodiment as shown FIG. 16, there may be an additional advantage in that less power is required to operate the system in comparison with the embodiment in FIG. 15.
However, in the known method for producing glass sands as above-described, a device is utilized as the secondary crusher 10 which may crush glass fragments which have been previously crushed by the primary crusher 3 to a certain degree, and thus there is a limit on sizes of glass fragments which may be supplied from the primary crusher 3 into the secondary crusher 10 resulting in that a sorter 5 must be arranged below the primary crusher 3 so as to sort and exclude glass fragments of certain sizes (ex. 20 mm) or greater so that they may are not be supplied to the secondary sorter 10.
Additionally, the secondary crusher 10 in the known system has its internal surface formed by plying ceramic materials which have improved resistance against abrasion so that it may not be damaged by sharp glass edges which have been crushed by means of primary crusher 3. However, ceramic materials are very vulnerable to shock. Thus, if metallic materials are accidentally entrapped into this secondary crusher 10, the metallic materials may be repulsed by the secondary crushing means 14 so as to impinge against the ceramic surface, and thus ceramic material surfaces can be easily damaged. Therefore, there arises a need to reliably remove metallic foreign objects such as caps and nails etc., from the glass fragments to be introduced into the secondary crusher 10, resulting in that a magnetic screening device etc., must be installed.
Furthermore, the necessity for such ancillary equipment creates a problem that the entire system becomes bulky and expensive.
To solve the above-described problem, the present invention provide a method for producing glass sands, in which the method comprises steps of crushing the glass articles into finer glass fragments, agitating such glass fragments which have been finely crushed and treating glass fragments so that they contain no sharp edges while at the same time forming glass fragments into glass sands with predetermined grain-sizes, then, sieving foreign materials which have been entrapped into glass sands which have been formed as grains while simultaneously sorting glass sands according to their grain-sizes.